Biofertilizers and sustainable agriculture: exploring arbuscular mycorrhizal fungi (Applied Microbiology and Biotechnology,June 2017, Volume 101, Issue 12, pp 4871–4881)

Abstract:Worldwide agricultural food production has to double in 2050 so as to feed the global increasing population while reducing dependency on conventional chemical fertilizers plus pesticides. To accomplish this objective, there is the need to explore the several mutualistic interactions between plant roots and rhizosphere microbiome. Biofertilization is the process of boosting the abundance of microorganisms such as arbuscular mycorrhizal fungi (AMF) in the natural plant rhizosphere which depicts a beneficial alternative to chemical fertilization practices. Mineral nutrients uptake by AMF are plausible by means of transporters coded for by different genes and example include phosphate transporter. These fungi can be produced industrially using plant host and these, including the possibility of AMF contamination by other microorganism, are factors militating against large scale production of AMF. AMF isolates can be inoculated in the greenhouse or field, and it has been shown that AMF survival and colonization level were enhanced in soybeans grown on land that was previously cultivated with the same plant. Next generation sequencing (NGS) is now used to gain insight into how AMF interact with indigenous AMF and screen for beneficial microbial candidates. Besides application as biofertilizers, novel findings on AMF that could contribute to maintenance of agricultural development include AMF roles in controlling soil erosion, enhancing phytoremediation, and elimination of other organisms that may be harmful to crops through common mycelia network. The combination of these potentials when fully harnessed under agricultural scenario will help to sustain agriculture and boost food security globally...PDF enclosed

Functional Diversity of Mycorrhiza and Sustainable Agriculture

1st Edition

Management to Overcome Biotic and Abiotic Stresses

Authors: Michael Goss Mário Carvalho Isabel Brito

eBook ISBN: 9780128042861,Paperback ISBN: 9780128042441

Imprint: Academic Press,Published Date: 30th May 2017,Page Count: 254

Are mycorrhizal fungi our sustainable saviours? Considerations for achieving food security,DOI: 10.1111/1365-2745.12788

Summary

The 20th century saw dramatic increases in agricultural productivity, largely through the development and application of pesticides, fertilisers rich in nitrogen and phosphorus, and advances in plant breeding and genetic technologies. In the last 15 years, however, many key crop yields have plateaued. Climate change, an ever-increasing human population, depletion of global rock-phosphorus and growing energy prices make current fertiliser production unsustainable and represent sizeable challenges to global food security.

Many important crops form symbioses with arbuscular mycorrhizal fungi (AMF), and this has motivated the development of novel approaches in crop breeding and agricultural practices to support and promote AMF in agroecosystems.

Arbuscular mycorrhizal fungal symbiosis can be high beneficial in crops and wider agroecosystems in many ways, including improved soil structure and resistance to pests. However, AMF colonisation does not necessarily translate directly into enhanced plant performance or crop yield, while land management practices that would encourage mycorrhiza–crop associations, such as low-till or minimal chemical input often incur yield-reducing trade-offs.

Synthesis. We draw on ecological knowledge of AMF to inform their role in agroecosystems, providing a balanced look at mycorrhiza–crop symbioses in terms of plant ecophysiology and the wider role of AMF in agroecosystems and ask the question: are AMF our sustainable saviours?

Sustainable agriculture can be explained through the intersection of environmental performance and social performance and economic performance.

We found that under arid environment Glomus mosseae is the most effective species for arid crops and Glomus fasciculatum is the best species for arid trees and horticultural plants growing under arid regions. Large scale multiplication is a major problem of AM fungi because they are host specific. A major beneficial effect of mycorrhization on host plant growth is brought about by the increase in below ground combined surface area (roots and mycorrhizas) for acquisition of nutrients. Diverse beneficial mycorrhizal effect  can readily be demonstrated under controlled environmental conditions. The major limitations of predictions is our poor knowledge of the functioning of the associations under field conditions.Therefore, more systematic studies are required to exact computation of their benefit .

Sustainability , i doubt , we can look through an isolated window.Sustainability considers agroecology, production economics, natural resource conservation, livelihood security, up to secondary agriculture...Colleagues have rightly highlighted this issue..

Sustainable agriculture is implemented through an integrated concept of production. Do I have enough material on this production if you are interested?.

Much of the work on mycorrhizae have been focused on laboratory and greenhouse studies which are not necessarily transferable to field environments. In the field, since the vast majority of plants over 80% are mycorrhizal, the presence of a noninoculated and noninfected control is not available. Many times the benefits of mycorrhizae are expressed when plants are under stress. For instance, the deficiency of P is favorable to have greater mycorrhizal initiation and development. The advantage of mycorrhizal plants is especially noted under conditions of drought stress. In North America, drought might curtail yield of maize significantly only 1 year in 4 years. A short-term experimental approach does not let its effect be measured. Another phenomenon is that not all species and strains give the same results.  There is still much work that is needed to make mycorrhizal practical for enhancing our agricultural systems globally. 

We have several ecological regions in the word and agro-climatic region in India where functional mycorrhizal diversity has not been properly worked out. It is very difficult to state which species is Nobel without knowing the ecological regions and microbe-microbe interaction with host plants. Functional diversity and efficacy of mycorrhiza in agriculture system depends upon studying interaction with other microbes in the rhizosphere as well as soil-microbe interactions. Such studies are still not in shape to conclude at the field level although there are plethora of reports on laboratory experiment basis or in isolation as compared to field basis.  

Since the best soils around the world have developed under grasslands, the perennial grassland with mixed species is particularly noble or compelling for sustainable and regenerative agriculture. The grasslands give rise to large ruminants which are part of the equation of peak soil environment. This natural system is mimicked by mixed animal and crop agriculture where manures are repatriated into the systems. Perennials and manures will favor the critical fauna and flora such as earthworms and positive microbes such as Rhizobium bacteria and mycorrhizal fungi for instance. Since grasslands can have a need for nitrogen the ability of fertilizer nitrogen can be avoided by concentrating on the roles of legumes both in the forage or ley systems and also in the cropping time. The ability of legumes is to address both the depleted soil carbon while simultaneously addressing soil nitrogen deficit.  Since many of crop soil issues are tillage related the use of mixed system reduces any need for continuous tillage and also optimized positive sequestration from increases soil organic and lowering the "need" for ammoniated nitrogen which has side effects of increased soil organic matter decay, high carbon footprint, and significant acidification potential. Legumes and grass which are perennial and can be combined with ruminants which improve our diets are noble species for sustainable regenerative agriculture.